1. Field of the Invention
This invention relates to a medical catheter and guide wire which have high safety and improved operability and are advantageously used in a wide range of examination and treatment, especially in angiography, angioplasty, embolization, retriever/recovery of foreign body, and calculus capture.
2. Prior Art
Conventional catheters designed to be inserted into blood vessels and ureters for examination and treatment purposes include, for example, those used in angiography, intravascular medicament administration, intravascular surgery, ureterolithotomy, and endoscopic retrograde cholangiopancreatography (ERCP).
There have been proposed several catheters of this type including a tube of a flexible polymer having a leading metallic guide wire inserted therein, a tube of polyethylene having stainless steel wire braided in a mesh fashion, and a helically cut stainless steel tube enclosed in a synthetic resin (see JP-A 6-134034 and JP-A 7-96037).
However, in all cases of these conventional catheters, it has been difficult for operators to smoothly insert and guide them into complex and tortuous thin wall vessels and ureter to the target sites. Also, since they do not possess enough flexibility, suppleness, elasticity, and operability and other characteristics required for catheters, they always need the combined use of leading guide wires to complement the characteristics required for catheter bodies.
On the one hand, JP-A 8-257128 proposes a medical tube whose structure is shown in FIG. 37. It consists of a metal tube xe2x80x9ca,xe2x80x9d made of stainless steel, shape memory alloy, and the like, which has a groove or grooves shown as xe2x80x9cbxe2x80x9d on its distal end. The grooves are engraved into the shape of either a helix as a whole, or circles spaced apart at certain intervals, and may be separated at some points or other by connection regions without grooves. The outer surface of tube xe2x80x9caxe2x80x9d is covered with a resin coating or resin tube xe2x80x9cc.xe2x80x9d
Furthermore, JP-A-8-308933 proposes a medical tube whose structure is shown in FIG. 38. It consists of a metal tube xe2x80x9ca,xe2x80x9d whose distal portion is thinner-walled as compared with a proximal portion. The said distal portion has a groove or grooves xe2x80x9cb,xe2x80x9d which are engraved into the shape of either a continuous helix, or a helical shape as a whole, or circles spaced apart at certain intervals, and which may be separated at some points or other by connection regions without grooves. The outer surface of the said tube xe2x80x9caxe2x80x9d is covered with a resin coating or resin tube xe2x80x9cc.xe2x80x9d
In these medical tubes, the radial or helical grooves in the distal portion confer some degree of flexibility, but not to a satisfactory extent. When the tubes are advanced into complex tortuous blood vessels and ureters, the distal portion can break or fail. Additionally, the outer resin tube or resin coating can be caught in the grooves. In particular, the metal tube whose distal portion is thinner-walled as in JP-A 8-308933 can be more readily broken. These medical tubes are thus not satisfactory in terms of safety and operability.
Moreover, JP-A 3-188875 discloses a catheter comprising a body portion and a distal portion with an internal lumen wherein at least the said body portion is made of a superelastic metal tube.
However, since this catheter has superelastic effect due to the superelasticity of the said metal tube, the problem of blood vessel damages such as rupture, perforation, dissection and so on may arise. This is because if the distal portion is brought into contact with a part of the blood vessel and applies inadvertent force there, it will deform the vessel, and when the stress is removed, due to the superelasticity of the tube, it will immediately recover the original state resulting in the damages of the said blood vessel.
To solve this problem, a catheter has been proposed in which a leading tube formed mainly of a thermoplastic polymer and of several millimeters to several centimeters long is attached to the distal end of a conventional catheter.
The catheter having the said thermoplastic tube attached to the distal end, however, has a step-like structure at the boundary between the thermoplastic resin tube at the distal end and the metallic catheter body trailing the rear end of the tube, resulting in losses of operability and safety.
Specifically, the catheter having a leading tube by thermoplastic resin at the distal end does not exhibit fully satisfactory performance where the boundary between the thermoplastic resin tube at the distal end and the metallic catheter body trailing the rear end of the tube contacts against the wall of a complex tortuous blood vessel or ureter. The distal portion made of the flexible thermoplastic resin can enter the sharply bent blood vessel or ureter, but the subsequently advancing boundary with the metallic catheter body comes in contact with the blood vessel wall, whereby the distal portion of the catheter can broken or damaged at the boundary. This causes pain or abnormal feeling and sometimes can cause damage to the sensitive blood vessel or ureter.
Recently, in the treatment of arteriovenous malformation (AVM), embolization using an embolic material such as isobutyl cyanoacrylate (IBCA), n-butyl cyanoacrylate (NBCA) or ethylene-vinyl alcohol copolymer (EVAL) has achieved favorable results without hemorrhage. A great attention is paid to this embolization.
However, the embolization using an embolic material gives rise to a problem associated with injection of the embolic material. Since the embolic material is injected from the distal outlet of the catheter without blocking the blood flow, the embolic material can solidify in a state bonded to the catheter distal end, which prevents withdrawal of the catheter.
Further, up to the present, the only method for blocking blood flow for treatment purposes which can be used in practice is the use of a balloon catheter having a balloon attached to the distal end thereof.
For the blockage of blood flow using a balloon catheter, there is known a method involving heat fusing a balloon made of such material as silicone rubber, latex, or the like, to the distal end of a catheter, and injecting saline containing a contrast medium into the balloon through the catheter body to inflate the balloon at the distal end of the catheter to block the blood flow. Alternatively, a flowpath for injecting saline containing a contrast medium may be provided separately from the catheter body, and saline containing a contrast medium is injected into the balloon through the flowpath to inflate the balloon to block the blood flow.
However, the said balloon catheter with a separate flowpath results in a larger diameter which makes it difficult for the operator to insert it smoothly into a narrow blood vessel, ureter, pancreatic duct or bile duct (with a diameter of less than 2 mm). Also, because of structural restrictions of the balloon catheter, it is impossible to discharge the embolic material or contrast medium from the distal end of the catheter while blocking the blood flow.
There has been an embolization treatment wherein a guide wire having a distal head with a large diameter or a dilated projection is inserted into the catheter lumen for pushing out and implanting an embolic material such as a coil and the like at the target site.
However, when the above method is applied to a complex tortuous thin wall blood vessel, ureter, pancreatic duct or bile duct, it is sometimes impossible to smoothly insert the guide wire or to implant an embolic material such as a coil at the target site because the catheter body and guide wire may have strong rebounding or repulsive forces and lack flexibility.
Furthermore, as a catheter for retrieving and recovering foreign matter and a catheter for capturing calculus in the kidney or ureter, there has recently been proposed a catheter in which an operating part (or guide wire) having a foreign matter retrieving/recovering means or calculus capturing means at its distal end is inserted through its lumen (see JP-A 61-115550).
The said foreign matter retrieving/recovering and calculus capturing catheters lack flexibility and possess a strong restoring force because their catheter body is formed of a resinous tube or a metallic tube of stainless steel or superelastic metal. The operating part (or guide wire) trailing the foreign matter retrieving/recovering means or calculus capturing means also possesses strong rebounding or repulsive forces and lacks flexibility. As a result, when the above catheter is applied to a complex tortuous thin wall ureter, it is difficult to smoothly insert the catheter and carry the foreign matter retrieving/recovering means or calculus capturing means to the destination, failing to take full advantage of the foreign matter retrieving/recovering means or calculus capturing means.
As described above, the catheters and guide wires used in a wide range of examination and treatment, especially in embolization, angioplasty, angiography, retrieving/recovering of foreign matter, and calculus capture have several problems. It is desired to have a catheter and guide wire which facilitate a wide range of examination and treatment in a more safe and reliable manner.
The present invention has been made under the above-described circumstances, and its primary object is to provide a catheter which is constructed such that a catheter body has a distal portion and a proximal portion, at least the distal portion being free from superelasticity or pseudoelasticity while retaining the shape memory property, the proximal portion having rigidity, whereby the catheter has flexibility, suppleness and elasticity sufficient for eliminating a need for a leading guide wire for manipulation, resulting in improved safety and operability.
A second object of the invention is to provide a catheter which eliminates any step-like structure at the junction between a leading tube made of thermoplastic resin and a catheter body, minimizing the induction of unusual feeling and pain, and preventing damages of a blood vessel during operation as much as possible.
A third object of the invention is to provide a catheter which can be smoothly inserted into even a complex tortuous thin wall vessel, ureter, pancreatic duct or bile duct, ensures to block the blood or fluid flow at the destination, and enables angiography of blood vessels or embolization of lesions in a safe and reliable manner while maintaining the blocking of the blood flow.
A fourth object of the invention is to provide a catheter whose body has slits so that the body is formed as one-piece from the distal end to the proximal end eliminating the need for a leading tube made of thermoplastic resin, without a step-like structure, is unlikely to be broken, is improved in operability and safety, and is improved in manufacture cost performance in that the catheter diameter can be readily adjusted in accordance with the size of the destination.
A fifth object of the invention is to provide a catheter and a guide wire whose combination is effective for carrying out embolization, angiography, and foreign matter retrieval/recovery in a safe and reliable manner.
To attain the above objects, the present invention provides the catheter and guide wire defined below.
A first aspect provides a catheter characterized in that at least a distal end portion of a catheter body is formed of a shape memory-specialized alloy which has been so manufactured that it retains shape memory property, but free from superelasticity or pseudoelasticity at least at the body temperature.
In the catheter according to the first aspect of the invention, since at least the distal end portion of the catheter body is formed of a shape memory-specialized alloy and deprived of a strong repulsive force due to superelastic or pseudoelastic effect, the catheter can be safely and smoothly inserted in conformity with the shape of a blood vessel at the destination owing to the shape memory, eliminating the possibility of damages of a blood vessel which would have been caused by the distal end portion of a catheter body if it had superelasticity or pseudoelasticity.
A second aspect provides a catheter comprising a catheter body, an outer polymer layer covering the outer surface of the catheter body, and a thermoplastic resin tube joined to the distal end of the catheter body, characterized in that the region extending from the distal end portion of the catheter body to at least a proximal end portion of the thermoplastic resin tube, is reinforced by winding and/or braiding a linear elastic material selected from among a metal wire, organic wire and inorganic wire, either in a mesh fashion or in a coil fashion, respectively, or attaching the linear elastic material along the axial direction, or any combination of the above.
According to the second aspect of the invention, the catheter eliminates any step-like structure at the junction between the leading tube made of thermoplastic resin and the catheter body, minimizes the induction of unusual feeling and pain, and prevents a blood vessel from being damaged during operation as much as possible.
A third aspect provides a catheter comprising a catheter body and an outer polymer layer covering the outer surface of the catheter body, characterized in that the outer polymer layer is projected forward, and the catheter body is provided at a distal end with an injection part having lumen perforated therein, wherein the forward projection of the outer polymer layer can be radially dilated by injecting an injection fluid such as saline, an embolic material or a contrast medium through the lumen into the interface between the injection part and the forward projection of the outer polymer layer to fill the interface therewith.
Unlike the prior art balloon catheter having an inflating balloon at the distal end, the catheter according to the third aspect of the invention is provided with an inflating space or gap within the distal end portion of the catheter itself wherein by injecting an injection fluid such as saline, an embolic material or a contrast medium into the space or gap, the distal end portion of the catheter is dilated outward. This eliminates the need for an extra balloon and a separate conduit for inflating the balloon, allows the catheter to be formed thin, and enables to block the blood flow and the like in a safe and reliable manner.
A fourth aspect provides a catheter comprising a catheter body and an outer polymer layer covering the outer surface of the catheter body, characterized in that the catheter body is provided with at least one slit extending axially from the distal end of the catheter body, and the gap of the slit is narrowed such that the catheter body is reduced in diameter toward the distal end.
The catheter according to the fourth aspect of the invention eliminates the need for a leading tube made of thermoplastic resin at the distal end or a step-like structure, is unlikely to be broken, is improved in operation and safety, and permits the catheter diameter to be readily adjusted in accordance with the size of the destination.
A fifth aspect provides a guide wire comprising a guide wire body and a distal head and adapted to be inserted into a catheter lumen, characterized in that the distal head of the guide wire is configured to a shape capable of pushing out an embolic material such as a coil, and at least a distal end portion of the guide wire body is formed of a shape memory-specialized alloy having shape memory property, but free from superelasticity or pseudoelasticity at least at the body temperature.
Since at least the distal portion of the guide wire body is formed of a shape memory-specialized alloy having shape memory property, but free from superelasticity or pseudoelasticity at least at the body temperature, the guide wire according to the fifth aspect of the invention can be smoothly inserted into even a complex tortuous thin wall vessel without the risk of the guide wire caught by the catheter lumen. This ensures that the expanded distal head pushes out an embolic material such as a coil so that the embolic material may be implanted at the destination within the living body.